8D PROBLEM SOLVING – GIẢI QUYẾT VẤN ĐỀ HIỆU QUẢ VỚI…

1. SPC la gi? Statistical Process Control

SPC (Statistical Process Control) la kiem soat qua trinh thong ke — su dung bieu do kiem soat (Control Chart) de theo doi bien dong qua trinh theo thoi gian thuc. SPC phan biet:

• Common cause: Bien dong tu nhien, co hu trong quy trinh. Can thay doi quy trinh de giam.
• Special cause: Bien dong bat thuong do nguyen nhan cu the. Co the tim va loai bo.

SPC la trai tim cua Kiem soat Qua trinh.

2. Cac loai Control Chart

• X-bar R: Du lieu lien tuc, mau nho (n<10). Pho bien nhat.
• X-bar S: Du lieu lien tuc, mau lon (n>=10).
• p-Chart: Ty le loi (%).
• c-Chart / u-Chart: Dem so loi tren don vi.
• EWMA / CUSUM: Phat hien dich chuyen nho.

3. Quy trinh SPC 6 buoc

1. Chon thong so critical: CTQ can theo doi.
2. MSA truoc: Dam bao he thong do dang tin cay.
3. Thu thap du lieu: 25-30 subgroup de ve baseline.
4. Ve Control Chart: Tinh CL, UCL, LCL. Ve len giay/phan mem.
5. Phan tich: Tim special cause, giam common cause.
6. Standardize: Reaction plan khi ngoai UCL/LCL.

4. Rules phat hien bat thuong (Western Electric)

• Rule 1: 1 diem ngoai ±3σ → dung may, kiem tra ngay.
• Rule 2: 9 diem lien tiep cung phia CL → dich chuyen trung binh.
• Rule 3: 6 diem lien tiep tang/giam → trend.
• Rule 4: 14 diem alternating → bimodal.
• Rule 5: 2/3 diem gan ±2σ → bien dong tang.

5. Ket qua tu SPC

• VinFast: SPC phat hien dich chuyen 2h truoc loi xay ra. OEE tu 62% len 87%.
• Samsung: SPC + MSA giup Cpk 0.89 -> 1.67.

6. Cau hoi thuong gap

SPC co can phan mem khong?

Co the ve bang tay (A0 paper). Phan mem (Minitab, SPC software) giup tu dong ve + tinh toan nhanh.

7. Lien he tu van SPC

Hotline: 098 905 1920 (Chi Dung)

Email: dung.truong@lean.vn

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